So you would say that all those guys with Rotary subs are doing it for the bragging rights? .

Rotary sub buyers aren't installing them for 1Hz performance

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But the whole point is so that I can apply a house curve into the single digits,

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as FOH pointed out earlier in this thread, the lower you go the louder it needs to be to be heard.

Where higher SPLs make lower frequencies 'audible' are in the mid to upper teens ie 15-16Hz not low single digits.
The frequencies you're talking about will never be 'heard' regardless of SPL, they will only be manifest as room vibration (shake). So it doesn't matter if the system is reproducing 1Hz or 8Hz no one will be able to tell the difference

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There would be 3 drivers on the left wall of the manifold and 3 drivers on the back wall of the manifold. Would this cancel vibrations?

They must be mounted in opposition to cancel the mechanical reactive forces

For what it's worth, my understanding is that movies are only encored down to 3Hz. Somebody please correct me if I'm wrong on that.

Well these movies all have LF extension to 2hz , Battle of LA, Star Trek, Tron, Batman Begins,The Dark Knight, 9, Amazing Spider-Man, Quantum of Solace and should I go on, b/c there are many more?

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Originally Posted by Thomas-W

Rotary sub buyers aren't installing them for 1Hz performance

Where higher SPLs make lower frequencies 'audible' are in the mid to upper teens ie 15-16Hz not low single digits.
The frequencies you're talking about will never be 'heard' regardless of SPL, they will only be manifest as room vibration (shake). So it doesn't matter if the system is reproducing 1Hz or 8Hz no one will be able to tell the difference
They must be mounted in opposition to cancel the mechanical reactive forces

Nor did I say I wanted 1hz performance. I said "No need for a rotary sub at all. Should get me flat to 1hz.", which means what it says, I may not need a Rotary Sub to flat to 1 hz, but then again I don't know how much that curve drops off after 2hz??? In any case having the head room to play that low would be welcomed by most who enjoy ULF I would think.
A quote from the Rotarywoofer.com/

"Want to hear what 5Hz sounds like? A new woofer technology unlike any other and a new product category for home audio. This is the first home audio woofer delivering true response to DC. The Thigpen Rotary Woofer is the worlds first true infrasonic home audio or home theater woofer. Conventional subwoofers roll off rapidly below 20Hz. With no cone the rotary woofer achieves high efficiency at very low frequencies. Most subwoofers have a difficult time producing acoustic output below 20Hz at audible levels. They generally require large amounts of equalization, distortion rises rapidly, and even the most expensive available cannot produce significant output below 10Hz. Subwoofer electronics usually contain a cutoff filter which sharply rolls off content to the subwoofer below 20Hz to protect the speaker. On the other hand, the rotary woofer has enough acoustic output to move an open door back and forth .5” between 1 and 5Hz! It has enough output to find resonance frequencies of walls and ceilings in a room. It requires no equalization to achieve flat response to below 1Hz. Microphones have low frequency capability that far exceeds the low frequency output of current subwoofers. In many cases infrasonic information is in a recording, it is not being reproduced by the sound system.
A missing link in sound reproduction. Experience special effects like never before. If you want to hear and feel the 11hz hertz fundamental frequency from a helicopter rotor, the low frequency rumble of wind, the space of a concert hall or infrasonic information contained in an explosion, this is the only woofer technology available. Over the years the generally accepted low frequency limit of hearing has been 20Hz, some suggesting 16Hz. However nothing existed to produce significant enough output to change this belief. This development will spawn new special effects and we will begin to understand the true low frequency limit of human hearing. The TRW-17 rotary woofer is now being used in theme park attractions, concert venues, professional audio applications and research projects."

And this is also from that web page and is was the reason why I thought that it was possible to hear ULF even in the single digits. 115db @ 3hz.. Is this graph wrong?

Thanks for the info on the opposing drivers, much appreciated.

BTW , I am no expert and I probably know as much about subs as you guys have forgotten. I just want a great experience while watching my favorite movies.

BTW , I am no expert and I probably know as much about subs as you guys have forgotten. I just want a great experience while watching my favorite movies.

Cheers Dave

Dave, at this point, I'm going to have to let someone smarter than I weigh in. Just keep in mind the drastically different methodologies behind either approach you decide on.

While adding 12 more RE XXX may potentially get you the same amount of extension as the TRW-17 down to 1Hz, I just want to again remind you of the intrinsic cost associated with adding that much more fire power:

While I consider myself an unwavering ULF enabler, and I'm all for helping you spend your money, even I seriously doubt that you will be able to ascertain a notable difference in an increase in output between 2.5Hz down to 1Hz… Definitely not $25K+ worth.

On the other hand… Right now, given you are at reference (let's call reference 105db) @ 2.5Hz with 4 RE XXX, If you purchased 9 additional RE XXX to supplement the 3 you have yet to install (total of 16 RE XXX), I think 117db @ 2.5Hz and a +12db gain accross the spectrum should be fun… Maybe even dangerous?

I've never experienced anything like that, so if that doesn't induce vertigo and/or nausea to your audience, I'm not sure what else will…

I've always wanted to visit Japan. 16 RE XXX might further justify the trip. If I do, I'll be sure to take my Airsickness bag with me from the plane.

Are you ever going to hit the limits of what you have now? If not I would save your cash. At the levels I listen to movies I am using maybe 10% of the headroom. I can't even see cone movement except on the heaviest LFE. REF level playback of any movie is nothing for it. Truthfully 4 would easily get the job done for me. All 8 gives me minimum short term output of >127dB from 6Hz on up which I have measured and in the process broke quite a few things throughout the house. Most of the range there is 135dB worth of headroom if not more. And I am amplifier not excursion limited. I would never listen to anything with this type of level in my home. Even the very short duration CEA-2010 tone bursts were uncomfortable and making me fear something would break which eventually happened at 32Hz when a large picture came off of the wall in the foyer and broke the frame and glass out of the front on the tile floor. That is just a split second burst signal.

Anyway what I am saying is if you really feel like you need more than 4, get 4 more for the back manifold. 8 is 104L of displacement. Forget liters or cc's that is over 3.5 cubic ft of air displacement. I am all for overkill but I dont see how you could ever need more than that. You would just be increasing the cost and complexity of the system for capabilities that will never be used.

Are you ever going to hit the limits of what you have now? If not I would save your cash. At the levels I listen to movies I am using maybe 10% of the headroom. I can't even see cone movement except on the heaviest LFE. REF level playback of any movie is nothing for it. Truthfully 4 would easily get the job done for me. All 8 gives me minimum short term output of >127dB from 6Hz on up which I have measured and in the process broke quite a few things throughout the house. Most of the range there is 135dB worth of headroom if not more. And I am amplifier not excursion limited. I would never listen to anything with this type of level in my home. Even the very short duration CEA-2010 tone bursts were uncomfortable and making me fear something would break which eventually happened at 32Hz when a large picture came off of the wall in the foyer and broke the frame and glass out of the front on the tile floor. That is just a split second burst signal.

Anyway what I am saying is if you really feel like you need more than 4, get 4 more for the back manifold. 8 is 104L of displacement. Forget liters or cc's that is over 3.5 cubic ft of air displacement. I am all for overkill but I dont see how you could ever need more than that. You would just be increasing the cost and complexity of the system for capabilities that will never be used.

My 2 cents

Werd. Well said, Josh.

Also, you're fighting an up hill battle, in the snow and with no shoes on chasing 1hz extension.

I would agree. I have half what you have and I have a tremendous amount of clean bass.

I have the 104L 8 pack Dave is talking about and it is totally excessive . Friends are picking their jaws up off the floor long before the drivers are even stretching their legs. Of course it does depend on the space you are in quite a bit but unless it is a gym or ballroom sized space...

BTW I just realized who you were the other day Mike. I was wondering where you had been and didnt know you had changed your handle.

I have the 104L 8 pack Dave is talking about and it is totally excessive . Friends are picking their jaws up off the floor long before the drivers are even stretching their legs. Of course it does depend on the space you are in quite a bit but unless it is a gym or ballroom sized space...

BTW I just realized who you were the other day Mike. I was wondering where you had been and didnt know you had changed your handle.

Hi Josh. I know what you mean about the drivers hardly moving and I don't have anything near what you have. I will play a bass heavy scene at reference and it has so much low end, that I get concerned, how much the drivers are moving (can't see them in the dark). So I turn on the lights and play the scene over again and the drivers are hardly moving.

Dave, at this point, I'm going to have to let someone smarter than I weigh in. Just keep in mind the drastically different methodologies behind either approach you decide on.

While adding 12 more RE XXX may potentially get you the same amount of extension as the TRW-17 down to 1Hz, I just want to again remind you of the intrinsic cost associated with adding that much more fire power:

While I consider myself an unwavering ULF enabler, and I'm all for helping you spend your money, even I seriously doubt that you will be able to ascertain a notable difference in an increase in output between 2.5Hz down to 1Hz… Definitely not $25K+ worth.

On the other hand… Right now, given you are at reference (let's call reference 105db) @ 2.5Hz with 4 RE XXX, If you purchased 9 additional RE XXX to supplement the 3 you have yet to install (total of 16 RE XXX), I think 117db @ 2.5Hz and a +12db gain accross the spectrum should be fun… Maybe even dangerous?

I've never experienced anything like that, so if that doesn't induce vertigo and/or nausea to your audience, I'm not sure what else will…

I've always wanted to visit Japan. 16 RE XXX might further justify the trip. If I do, I'll be sure to take my Airsickness bag with me from the plane.

That is the problem with me, I get confused with the doubling the power gets you X amount of db's and the doubling of drivers get you x amount addition db's. Those figures make it a lot clear thanks. And the thing is , that graph is not max SPL yet with the 4, the baffle wall and the room being what it is really boosts the ULF. Thanks for the detailed post.

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Originally Posted by Ricci

Dave,

Are you ever going to hit the limits of what you have now? If not I would save your cash. At the levels I listen to movies I am using maybe 10% of the headroom. I can't even see cone movement except on the heaviest LFE. REF level playback of any movie is nothing for it. Truthfully 4 would easily get the job done for me. All 8 gives me minimum short term output of >127dB from 6Hz on up which I have measured and in the process broke quite a few things throughout the house. Most of the range there is 135dB worth of headroom if not more. And I am amplifier not excursion limited. I would never listen to anything with this type of level in my home. Even the very short duration CEA-2010 tone bursts were uncomfortable and making me fear something would break which eventually happened at 32Hz when a large picture came off of the wall in the foyer and broke the frame and glass out of the front on the tile floor. That is just a split second burst signal.

Anyway what I am saying is if you really feel like you need more than 4, get 4 more for the back manifold. 8 is 104L of displacement. Forget liters or cc's that is over 3.5 cubic ft of air displacement. I am all for overkill but I dont see how you could ever need more than that. You would just be increasing the cost and complexity of the system for capabilities that will never be used.

My 2 cents

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Originally Posted by MKtheater

I have 36 liters of displacement which is more than any movie can give. I would bet even half that is overkill.

Thanks for the input Ricci & MK, it is hard to know when to stop, but I do want the IB at the back of the room to even the base out a bit more and I already have the drivers, so I guess I will stick with the plan of adding the drivers to back of the room to complement the front 4 drivers at the front and I won't worry about going with a 6 or 9 driver manifold, just stick with the line array I had planned. I know you are right about the complexity of integration, and since I will be the one integrating them I guess I better keep it simple.

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Originally Posted by Scott Simonian

Werd. Well said, Josh.

Also, you're fighting an up hill battle, in the snow and with no shoes on chasing 1hz extension.

Lucky I am off the Hokkaido for a sky trip next month, I may be able to try that out!!!!

I like the idea of adding more to smooth out response. Especially since it will be even more XXX18's.

However, expecting 1hz extension is unrealistic but not because you don't have the displacement capability. Not at all. It's all limited by electronics <5hz. I have never seen consumer equipment flat to DC that we'd use in an HT environment. There might be some device that can do it but not everything in the signal chain. Sooo... enjoy your 3hz extension.

You already have the other 3 drives? I would get a 4th and do an opposed design to balance out the forces. Also I assume you will use the same amplifier or model for the second set of 4 subs? That will keep your drive level matched for both sets of drives. If you go with three the impedance will be different and your gain structure and drive level of the 3 drivers will be different from the front four.

You already have the other 3 drives? I would get a 4th and do an opposed design to balance out the forces. Also I assume you will use the same amplifier or model for the second set of 4 subs? That will keep your drive level matched for both sets of drives. If you go with three the impedance will be different and your gain structure and drive level of the 3 drivers will be different from the front four.

Yes, I have the 3 drivers here. If I do a 4th, I will have to figure outr a way to mount them, but should not be a problem. Yes the amp will be the same.

On a different note, I need urgent advise.

I just was going through the RS20i setup menu and I realised that for my last movie I had played the entire movie with the 4 subs on the center channel. So I was feeding the subs a full range signal. Would this have damaged them? I did not watch the movie anywhere near reference levels.

Why I ask is b/c I went to test them in REW to see if I done some damage they they played them back I was getting all sorts of funky sounds, like scrapping sounds and vurtually no output at all. (I am using the beta HDMI REW)

But after playing a bit more I got the below measurements (Purposfully with low SPL) with the subs on a different channel. Does the below graph indicate any damage? (BTW, I was also playing around with the delays, so there may a few differences in the graph from the other day).

OK, after a bit of head scratching and consulting with the Engineer, I came up with a dual opposed design like this.

Will a staggered design like this work to cancel vibrations from the drivers?

This is the veiw from the back room, the drivers will be have their faces pointing into the room, since I don't have the height to do a 4 driver line array, this is the next best thing, sort like a huge outie design.

This is an interesting question Dave. I have always assumed that to truly benefit from the dual opposed design, the drivers had to be mounted directly opposite of the opposed driver. Great question. I look forward to those that know chiming in.

Keeping the drivers on common axes (the ˝normal" opposed design) would still be preferred, but the design you've shown should give you 90% of the benefit. You'll get a little twisting moment resultant that the ideal design doesn't have, but your relatively tall manifold will be fairly good at reacting that.

Is your sketch not to scale? It looks like the drivers are shallow enough that you could actually scoot them to common axes. Will that not work? I'm Aldo not sure of the cooling mechanism employed by these drivers, so that may be what's keeping you from aligning them.

Keeping the drivers on common axes (the ˝normal" opposed design) would still be preferred, but the design you've shown should give you 90% of the benefit. You'll get a little twisting moment resultant that the ideal design doesn't have, but your relatively tall manifold will be fairly good at reacting that.

Is your sketch not to scale? It looks like the drivers are shallow enough that you could actually scoot them to common axes. Will that not work? I'm Aldo not sure of the cooling mechanism employed by these drivers, so that may be what's keeping you from aligning them.

The sketch is pretty much to scale with placement, but the depth of the drivers are not. I have 24" wide opening and the drivers are nearly 15" deep, so a conventional opposing design is a no go.

If you could spare the height, another option would be to orient them like this:

>
<<br /> <<br /> >

As before, just put them as close together as you can. But because one pair of drivers isn't nested anymore, this has to be a little taller than your sketch. The advantage is that this configuration would be completely inert, just like the standard opposed setup.

But if there isn't room for that, don't worry. The option you presented is still good and gets you most of the benefit of the opposed design.

The basic idea is to have the top and bottom drivers facing the same way as each other. Then have the two middle drivers facing the other way. The middle two drivers wont nest together as well as in the alternating design, so that forces it to be a little taller. But if it still packages short enough to fit, it has the advantage of completely cancelling its own vibrations.

I have been playing with the LP and I moved it forward a tad and this is what I got. Safe to say I never imagined that moving the main listening position forward would change the in room response this much.
I purposefully bumped the area from 22hz and below, other wise it would be flat. The biggest win I found was that the waterfall plot .

My mic and or electronics fall off at 5hz as well but that does not mean I don't get to 3hz. I have not measured 3hz but I will take a sweep with THD and see. I just replaced my processor and amps so maybe I will have less rolloff, maybe. It looks good to me, you were +/- 6 dBs from 3.2 hz and up so I won't mess with it too much. I like the blue response better!